In a large mixing bowl, add sugar, flour and eggs, whisk well until combined.
Pour the milk into a saucepan and heat (not boiling). Once the milk becomes hot, add the vanilla extract, stir, then turn off the heat.
Now, pour the milk in a tiny stream over the flour mixture, constantly stirring.
Next, pour the mixture back into the saucepan over low heat and whisk vigorously until the mixture has thickened (for about 2-3 minutes), then remove from the heat.
Cover the custard with plastic wrap, stick the plastic wrap to the top of the custard to prevent forming crust or skin on the top. Then put it in the fridge.
Making the Bougatsa:
Preparations: Preheat the oven to 170C. Grease a 2030 cm baking tray with butter or line with parchment pepper.
Now, lay half of the filo sheets one by one on the baking tray and don't forget to brush each layer with melted butter. Then spread the custard equally on the top. Fold the filo sheet flaps over the custard.
Then top the custard with the rest of the filo sheets, brushing each layer with melted butter.
Next, use a sharp knife to cut the Bougatsa however you like, then brush the top with butter.
Bake it for 40-45 minutes or until crispy and golden brown.
Take the Bougatsa out of the oven and quickly sprinkle with the mix of powder sugar and ground cinnamon (cinnamon sugar), then serve.
Notes
To make sure the phyllo turns as crunchy as possible, place the baking tray/pan in the highest rank in the oven so the air can reach both the top and bottom of the pan/tray.
An easy way to cut Bougatsa is to use a pizza cutter or a sharp knife.